In applications requiring a high-gain antenna, there are at least three types of antennas that are typically employed, namely, a parabolic antenna, phased-array antenna, and a reflectarray antenna. The basic parabolic antenna includes a parabolic shaped reflector and a feed antenna located at the focus of the paraboloid and directed towards the reflector. The phased-array antenna includes multiple antennas with a feed network that provides a common signal to each of the antennas but with the relative phase of the common signal being fed to each of the antennas established such that the collective radiation pattern produced by the array of antennas is reinforced in one direction and suppressed in other directions, i.e., the beam is highly directional. In many applications, the phased-array antenna is preferred to the parabolic antenna because a phased-array antenna can be realized with a lower height profile relative to the parabolic antenna. However, the phased-array antenna typically requires a complicated and/or expensive feed network and amplifier structures. The basic reflectarray antenna includes a reflectarray that is flat or somewhat curved and a feed antenna directed towards the reflectarray. The reflectarray includes an array of radiating elements that each receive a signal from the feed antenna and reradiate the signal. Each of the radiating elements has a phase delay such that the collective reradiated signal produced by the array of radiating elements is in a desired direction. Importantly, the radiating elements are fed by the feed antenna. As such, relative to the phased-arrayed antenna, the reflectarray avoids the need for a feed network to provide a signal to each of the radiating elements.
An application that frequently requires a high-gain antenna is a space-related application in which the antenna is associated with a spacecraft, e.g., a communication or radar imaging satellite. Such space-related applications typically impose an additional requirement of deployability on the design of a high-gain antenna, i.e., the antenna needs to be able to transition from a stowed/undeployed state in which the antenna is inoperable or marginally operable to unstowed/deployed state in which the antenna is operable. As such, the high-gain antenna in these applications is coupled with a deployment mechanism that is used to transition the antenna from the stowed/undeployed state to the unstowed/deployed state. Characteristic of many space-related applications for such antennas is that the antenna and deployment mechanism occupy a small volume in the undeployed state relative to the volume occupied by the antenna and deployment mechanism in the deployed state.
One approach for realizing a deployable high-gain antenna suitable for use on a spacecraft is a parabolic antenna structure that includes a wire mesh reflector, a feed antenna, and a deployment mechanism. The deployment mechanism operates to transition: (a) the wire mesh reflector from a stowed state in which the reflector is folded to an unstowed state in which the reflector is supported in a paraboloid-like shape by a frame associated with the deployment mechanism and (b) the wire mesh reflector and the feed antenna from an inoperable stowed state in which the wire mesh reflector and feed antenna are not operably positioned relative to one another to an unstowed state in which the wire mesh reflector and feed antenna are operatively positioned relative to one another. Characteristic of such deployable parabolic antenna structures is a high part count and the need for a relatively large volume to accommodate the stowed wire mesh reflector, feed antenna, and deployment mechanism.
A second approach for realizing a deployable high-gain antenna suitable for use on a spacecraft is a reflectarray antenna structure that includes a two-layer reflectarray membrane, a feed antenna, and an inflatable deployment mechanism. The inflatable deployment mechanism operates to transition: (a) the reflectarray membrane from a stowed state in which the membrane is folded to an unstowed state in which the inflated deployment mechanism forms a frame that is used in tensioning the reflectarray membrane into a flat shape, similar to trampoline and (b) the reflectarray membrane and the feed antenna from an inoperable stowed state in which the reflectarray membrane and feed antenna are not operably positioned with respect to one another to an unstowed state in which the reflectarray membrane and the feed antenna are operably positioned relative to one another. Characteristic of such a deployable reflectarray are difficulties in understanding the deployment kinematics and reliability challenges, particularly in space-based applications.